A number of modular skylight systems are commercially available. These skylight systems include a plurality of building blocks including individual skylights which are assembled together as required to form a roof structure. In effect, each of the skylights acts as a roof, and each requires some mechanism for draining rain which is collected over the surface area of the skylight. Generally, the drainage or guttering system is custom fabricated from stock channels at the job site. This custom fabrication requires equipment for on-site welding. It is to be understood that welding of such gutters and in particular aluminum gutters, on site, requires very heavy equipment and is a time consuming and expensive process. Accordingly, it is preferable that such welding be kept to a minimum and occur in a shop environment.